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Hello there.

After running an 1H-NMR experiment I observed the acetic acid-d4 solvent peaks at 11.54 and 21.16 ppm (off the expected values by ~9 ppm to lower fields).

Is it possible that the lock was made onto the wrong deuterium acetic acid-d4 signal?

Please, advice.

asked Apr 07 '10 at 21:11

BONA's gravatar image


updated Apr 07 '10 at 22:13

Evgeny%20Fadeev's gravatar image

Evgeny Fadeev

hey, Bona. Edited up the title to make is sound more like a question - Evgeny Fadeev (Apr 07 '10 at 22:09)

yes it is possible to lock on one signal or the other if your solvent has two resonances. What kind of spectrometer are you using? This may help somebody answering your question. - Evgeny Fadeev (Apr 07 '10 at 22:46)

Thanks, The instrument is a 400 MHz Varian Mercury; however, I am observing the same with the 300 MHz Varian Mercury - BONA (Apr 08 '10 at 07:24)

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Well, you just need to reference the spectrum - they cannot always be automatically referenced (an actually most of the time you need to enter a small correction manually)

On older systems with vnmr software you'd type wft ds, then put the cursor on the reference peak (CD2H in your case), hit ref button and type in the chemical shift from the table.

Also you might want to check the solvent parameter - it does affect referencing. Just type solvent?. However in the end it's referencing what really matters, setting solvent parameter correctly may get you into the approximate range of correct referencing, but you'll still have to fix it up - especially if you have a mixed solvent.

edit: actually, I've missed an important point - if the transmitter frequency is set outside the "spectral window" of your compound - let's say just outside one of the edges of the spectrum (say left) - then some peaks from near the right edge will fold over and will show up at the left of your measured spectrum. To check if you have this situation - double the spectral window and see if any peaks move. If they do - move transmitter frequency to the middle of your spectrum.


answered Apr 08 '10 at 08:33

Evgeny%20Fadeev's gravatar image

Evgeny Fadeev

updated Apr 12 '10 at 15:08

Thanks for the answer. Let me understand please. I could manually reference the CD2HCOOD peak to its correct value using any NMR-processing software without having to re-run the experiment, am I right?. - BONA (Apr 09 '10 at 08:49)

sure you can. It's not a problem at all. - Evgeny Fadeev (Apr 12 '10 at 09:12)

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